An automatic bowling pin setting apparatus of known type is used in bowling alleys, setting ten pins in a triangular pattern on a pin deck. When pins remain upright after the first shot, they are picked up vertically and, after the pins that have been knocked down have been removed by a horizontal movement of the sweep barrier over the pin deck, are replaced for the second shot in the positions they were in after the first shot (possibly "off-spot").
To put down ten pins prior to the first shot in a frame of shots, the set up frame, comprising ten pin bins each holding a pin, moves down, the pin bins tilting into the vertical position and the pins being taken hold of by shutters locking around the necks of the pins. Once the pins are positioned on the deck, the shutters open and the set up frame moves upwards again. After the first shot the set up frame moves downwards onto the pins. Detectors equipped with electrical switches detect which pins have been knocked down and show the score on an electrical score board. Tongs which are mounted on the set up frame and driven by an electric motor mounted on the set up frame lock around the necks of the pins that have remained upright. Then the set up frame moves upward to enable the sweep barrier to sweep the pins that have been knocked down to the end of the pin deck onto a wide rotating belt which feeds the pins to the elevator. When the sweep barrier has returned to its position in front of the pin deck, the set up frame moves downward to reposition the pins which were lifted temporarily. Then the set up frame moves upwards again to be filled completely.
The sweep wagon is mounted in side gutters of the machine frame by means of wheels and prior to the first shot is held in a raised position so that the lane is clear for a ball to roll to the pin deck. When the ball passes a ray of light that is provided at a distance of about one meter before the first pin, a magnet on a member of the sweep barrier control mechanism is attracted in such a way that a hook at the end of the member will tilt, thus releasing the sweep barrier which will come down and can be moved backwards and forwards again by means of driving rods which are driven by a sweep barrier motor via a transverse crank shaft. The apparatus comprises an electronic control system.
A disadvantage of the known apparatus is that the drive line of the set up frame is long and complicated and, moreover, the drive of the sweep barrier, where it concerns lifting the sweep barrier to move it out of the path of an approaching ball, is taken off the drive of the set up frame. A set up frame motor comprising an electromagnetic brake drives a gear box via a V belt. By means of a chain a big open chainwheel is driven which also serves as a crank wheel for lifting the sweep barrier. The shaft of the big chainwheel extends right through the frame to the other side of the machine for operating a crank arm, the crank comprising a journal with a chain. This chain runs over a gear wheel mounted on top of a so-called tower comprising one of the pipe-shaped columns and is connected to this column by means of a freewheel coupling permitting the set up frame to be lowered either to the level of the pin deck or to the upper level of the pins standing on the pin deck. When the set up frame is moved up and down, via the rack of this column a pinion is operated. The shaft of this pinion extends right through the machine frame to a similar pinion meshing with the rack of the second column arranged at the other end of the machine.
The disadvantages of this long drive line to the two columns on opposite sides of the set up frame are:
a. Due to play developing after only a relatively short time in the plastic gears of both the gear box and the drive of the rack, slack in the chains and torsion in the long transverse driving shafts, uneven drive transmission to the left-hand and the right-hand part of the set up frame will occur, causing the set up frame to lean and increasing the chance of faults in detecting and replacing pins that were not knocked down after the first shot.
b. In the case of chain fracture, the set up frame will crash, and if any pins are present on the pin deck at the time, the columns of the set up frame and their guiding parts will be severely damaged.
c. Due to metal fatigue developing in the driving shafts in the course of time, their torsion strength will also decrease, thus rendering adjustment of the set up frame more difficult.
A drawback of the known apparatus as far as the control of the sweep barrier is concerned is the following. As observed above, the drive of the sweep barrier is partly taken off the drive of the set up frame, namely off the big open chainwheel, which serves as a driving crank wheel for picking up the sweep barrier. For that purpose a crankpin is welded onto the big chainwheel, which crankpin, via a chain, drives a member with a hook, which member is adapted for up and down movement at an angle to the horizontal. The hook can engage the suspension of the sweep barrier. This fairly complicated composite injection-moulded member lifts the sweep barrier when it is in the frontmost position after the first and after the second shot. Because the sweep barrier is lifted from a stationary position by a rotating crank wheel, periodically abrupt traction forces will be exerted generating shockloads in the apparatus. The sweep barrier is lowered by gravity, the fall of the barrier being dampened by a damper device.
The drive of the sweep barrier in respect of its backward and forward movement over the pin deck is powered by its own motor. The rotary movement of the sweep barrier motor, comprising a mechanical motor brake, is converted to a linear movement by means of cranks. Serious problems in adjusting the machine will arise due to the fact that the right-hand crank arm is detachably mounted onto the transverse shaft of the sweep carrier and play in this connection will develop soon. Long arms connected to this transverse shaft and used for moving the sweep barrier forwards and backwards, can tear easily at the joints.